Process for forming dye images

ABSTRACT

FORMAZAN DYE IMAGE DENSITIES FORMED BY TREATING A PHOTOGRAPHIC METAL IMAGE IN A HYDROPHILIC COLLOID BINDER LAYER WITH A TETRAZOLIUM SALT SOLUTION IN THE PRESENCE OF A METAL COMPLEXING LIGAND ARE ENCHANCED BY THE PRESENCE IN SAID BINDER LAYER OF A DISPERSION OF AT LEAST ONE HIGHBOILING SUBSTANTIALLY COLORLESS, CRYSTALLOIDAL ORGANIC OIL, THE WEIGHT RATIO OF OIL TO HYDROPHILIC COLLOID PREFEREABLY BEING IN THE RANGE OF FROM ABOUT 10:1 TO ABOUT 1:30 AND THE DISPERSED PARTICLES OF THE OIL PREFERABLY HAVING DIAMETERS IN THE RANGE UP TO ABOUT 2U.

United States Patent 01 3,676,135 Patented July 11, 1972 3,676,135PROCESS FOR FORMING DYE IMAGES Walter J. Musliner, Rochester, N.Y.,assignor to Eastman Kodak Company, Rochester, NY. No Drawing. Filed June22, 1970, Ser. No. 48,546

Int. Cl. G03c 7/00 us. or. 96-54 14 Claims ABSTRACT OF THE DISCLOSUREThis invention is related to photography, photographic elements,compositions for use in photographic processing and photographicprocesses for forming high density dye images from photographic metalimages.

In photography, it is sometimes desired to convert a photographic metalimage into a dye image or to add to a photographic silver image acorresponding dye image. Processes are desired that will make itpossible to obtain photographic reproductions having good imagedensities with elements containing less silver than usual or withphotographic silver images having lower image densities than needed. 'Ifa dye image alone is desired, it is necessary to provide a convenientmethod for removing the metallic 1mage.

Processes have been described in British Pat. 908,299 in which a silverimage in a photographic emulsion layer is converted into a formazan dyeimage .by treating the silver image with a tetrazolium salt in thepresence of cyanide ions and, subsequently, bleaching the image with aferricyanide bromide bleach bath, followed by washing, fixing with asodium thiosulfate bath, washing and drying. It is desired to preparehigher density dye images from metal images than is possible from theprior art processes.

It is an object of my invention to provide a novel process forconverting a novel photographic metal image in the presence of certainorganic oils into a higher density dye image than is possible with theprior art processes and preferably without using cyanide ions andwithout a separate bleach step and a separate fixing step.

Another object of my invention is to provide a novel, single-stepprocess for converting a metal image to a high density formazan dyeimage and, simultaneously, to remove the metal image from ablack-and-white developed photographic element.

Still another object of my invention is to provide a novel method whichis valuable for the conversion of even a low density silver image into aformazan dye image of a density higher than previously realized with thesame dyes.

Still another object of my invention is to enhance an image or improvethe image contrast obtainable from a silver image alone, by the use ofhigh density formazan dye images. 1 i

Still another object of my invention is to provide a novel photographicelement for producing silver images which are convertible to formazandye images of higher density and higher covering power than formazan dyeimages produced from silver images in elements outside my invention.

Still other objects of my invention will become apparent from aconsideration of the following specification and claims.

These and still other objects of my invention are accomplished by makingmy novel photographic element comprising a support coated with at leastone hydrophilic colloid layer containing a dispersion of light-sensitivemetal salt, preferably, silver halide grains and a dispersion ofparticles of a high-boiling crystalloidal organic oil that issubstantially solute-free (i.e., contains substantially no dissolvedmaterial, e.g., color-forming couplers, dyes, ultraviolet-absorbingcompounds, brightening agents, etc.), and using this photographicelement which contains substantially no color-forming coupler to make ametal image with a standard oxidation potential more positive than -0.98volt and then replacing at least part of this metal image with aformazan dye image by contacting the metal image with an aqueoussolution of a tetrazolium salt (T-salt) until the T-salt oxidizes themetal image to a metal ion and the T-salt is reduced to thecorresponding formazan dye in situ. The T-salt is used in the presenceof a metal complexing ligand that forms a metal complex. This metalcomplexing ligand is either (1) a separate compound in the T-saltsolution or (2) a moiety of the T-salt molecule, or the complexingfunction is filled by a combination of (1) and (2). The formazan dyewhich is produced from the T-salt is nondilfusible and replaces at leasta portion of the metal image.

The formazan dye image formed remains at the site of the original zerovalent metal image that has been converted to a metal ion. The metal ionis complexed as part of the formazan dye when the T-salt (and formazandye formed from it) contains a moiety that is a metal ion complexingagent, or the metal ion is removed by a fixing step or the use of acomplexing agent which renders the metal ion solution and which ispresent in the T-salt solution. Alternatively, the metal ion isreconverted to the zero valent metal image by a subsequent reductionstep so the formazan dye image formed previously is supplemented by ametallic image.

My invention is characterized by forming an insoluble formazan dye imageat the site of a zero valent metal image in a hydrophilic colloid binderand in the presence of a dispersion of at least one high-boilingcrystalloidal organic oil that is preferably substantially colorless. Myorganic oils have molecules that contain at least one polar group suchas an ester group, an amide group, an imide group, a ketone group, ahydroxyl group, an oxygen ether group and a halogen atom. The particlesof dispersed organic oils used in my photographic elementsadvantageously have diameters in the range up to about 2 and preferablyin the range up to about I in diameter. The weight ratio of my organicoil to the hydrophilic colloid binder is advantageously in the range offrom about 1:0.1 to about 1:30 with a preferred range of from about 1:1to about 1:35. The presence of my dispersed organic oil in a hydrophiliccolloid layer with a zero valent metal image, produces a valuableincrease in the formazan dye image density, especially in the D that isobtained from a given zero valent metal image density. The zero valentmetal image is advantageously formed in any photographic elementcontaining an appropriate light-sensitive metal salt prepared in ahydrophilic colloid binder that contains one of my high-boilingcrystalloidal organic oils.

In accordance with my invention, I have found that the above objects areaccomplished by forming formazan dye images in hydrophilic colloidlayers from metal images in the presence of a dispersion of at least onehigh-boiling (i.e., above about 175 C.) crystalloidal organic oilsrepresented by the following formulas:

wherein R R R R R and R each represent the same or a diiferent member,e.g., hydrogen, halogen (e.g., chlorine, bromine, fluorine, etc.), analkyl group of from 1 to 20 carbons (e.g., methyl, ethyl, propyl, butyl,amyl, phytyl, etc.), a phenyl group (e.g., phenyl, tolyl, chlorophenyl,etc.), an alkoxy group of from 1 to 20 carbons (e.g., methoxy, ethoxy,phytyloxy, etc.), a phenoxy group (e.g., phenoxy, tolyloxy, etc.);

R (II) 2 (H) wherein R and R are as defined previously and R representsa group, such as, an alkyl group of from 1 to 20 carbons (e.g., methyl,ethyl, propyl, butyl, hexyl, phytyl, etc.), an aryl group, such as, aphenyl group (e.g., phenyl, tolyl, ethylphenyl, chlorophenyl,methoxyphenyl, etc.), etc.;

u and wherein R and R represent the same or different group, such as, analkyl group of from 1 to 20 carbons (e.g., methyl, ethyl, propyl,2,3-dihydroxypropyl, butyl, decyl, pentadecyl, nonadecyl, benzyl, etc.),an aryl group [e.g., a phenyl group (e.g., phenyl, tolyl, ethylphenyl,amylphenyl, methoxyphenyl, ethoxyphenyl, chlorophenyl, dichloropehnyl,etc.), a-naphthyl, B-naphthyl, etc.]; R represents a group, such as, analkyl of from 1 to 20 carbons (e.g., methyl, benzyl, ethyl, butyl,hexyl, butoxymethyl, methoxyethyl ethoxymethyl, pentadecyl, nonadecyl,etc.), an aryl group [e.g., a phenyl group (e.g., phenyl, tolyl,ethylphenyl, chlorophenyl, methoxyphenyl, etc.), anaphthyl, fi-naphthyl,etc.], and L represents a divalent group, e.g.,

-CH OH 0 CHzO 1R1 group and a group wheerin R and R are as definedpreviously and n rep resents an integer of from 2 to 3;

o 0 ll Ru0 ZCOR3 wherein R is as described previously, Z represents agroup, such as, -CH=CH-, (CH etc.; in represents an integer of from 1 to10; R represents a group such as is defined for R ORB m wherein R and Rare as defined previously and R represents a member such as hydrogen, analkyl group of from 1 to 20 carbons (e.g., methyl, ethyl, butyl,dodecyl, phytyl, etc.), an alkoxy group of from 1 to 20 carbons (e.g.,methoxy, ethoxy, butoxy, phytyloxy, etc.), a halogen atom (e.g.,clorine, bromine, fluorine, etc.);

(VII) 0 wherein R is a defined previously; R represents a member, suchas, hydrogen, an alkyl group of from 1 to 20 carbons (e.g., methyl,ethyl, butyl, phytyl, benzyl, phenethyl, etc.), an aryl group [e.g., aphenyl group (e.g., phenyl, tolyl, butylphenyl, methoxyphenyl,chlorophenyl, etc.), a naphthyl group (e.g., a-naphthyl, ,6- naphthyl,etc.)] and nonmetallic atoms which, taken together with R and thenitrogen atom between R and R from a 5- to 6-membered heterocyclic ring(e.g., a piperidyl group, a morpholinyl group, etc.), and R represents amember, such as, hydrogen, an alkyl group of from 1 to 20 carbons (e.g.,methyl, ethyl, butyl, phytyl, benzyl, phenethyl, etc.), an aryl group[e.g., a phenyl group (e.g., phenyl, tolyl, butylphenyl, methoxyphenyl,chlorophenyl, etc.), a naphthyl group (e.g., rat-naphthyl, ,B-naphthyl,etc.)] and the nonmetallic atoms which when taken together with R andthe nitrogen between R and R12, form a 5- to 6-membered heterocyclicring (e.g., a piperidyl group, a morpholinyl group, etc.);

wherein Z, R and R are as defined previously; R represents a member,such as, hydrogen, an alkyl group of from 1 to 20 carbons (e.g., methyl,ethyl, butyl, phytyl, benzyl, phenethyl, etc.), an aryl group [e.g., aphenyl group (e.g., phenyl, tolyl, butylphenyl, methoxyphenyl,chlorophenyl, etc.), a naphthyl group (e.g., a-naphthyl, fl-naphthyl,etc.)] and nonmetallic atoms which, taken together with R and thenitrogen atom between R and R form 5- to 6-membered heterocyclic ring(e.g., a piperidyl group, a morpholinyl group, etc.), and R represents amember, such as, hydrogen, an alkyl group of from 1 to 20 carbons (e.g.,methyl, ethyl, butyl, phytyl, benzyl, phenethyl, etc.), an aryl group[e.g., a phenyl group (e.g., phenyl, tolyl, butylphenyl, methoxyphenyl,chlorophenyl, etc.), a naphthayl group (e.g., 0cnaphthyl, fl-naphthyl,etc.] and the nonmetallic atoms which, when taken together with R andthe nitrogen between R and R form a 5- to 6-membered heterocyclic ring(e.g., a piperidyl group, a morpholinyl groun. etc.);

wherein R is as defined previously and D represents a divalent group,such as, -(CH CH=CH-,

where R-, is as defined previously and R represents an alkyl group offrom 8 to carbons (e.g., octyl, decyl, dodecyl, pentadecyl, octadecyl,etc.), an aryl group [e.g., a phenyl group, (e.g., phenyl, tolyl,ethylphenyl, amylphenyl, methoxyphenyl, ethoxyphenyl, chlorophenyl,dichlorophenyl, etc.), a-naphthyl, ,B-naphthyl, etc.];

wherein R represents an alkyl group of from 7 to 20 carbons (e.g.,octyl, decyl, dodccyl, pentadecyl, octadecyl, butylphenoxyethyl,octyloxyethyl, benzyl, a-hexylbenzyl, etc.), a 4-alkylaryl group inwhich the alkyl group has from 1 to 20 carbons [a 4-alkylphenyl group(e.g., 4-amylphenyl, 2,4-diamylphenyl, 4-methylphenyl, 4-dodecylphenyl,4 dodecyl 2 chlorophenyl, 4-amyl-2-methoxyphenyl, etc.), a4-alkylnaphthyl group (e.g., 4-methyl-u-naphthyl, 4-dodecyl-u-naphthyl,etc.); and

wherein R represents an alkyl group of from 1 to 20 carbons (e.g.,methyl, ethyl, butyl, octyl, phytyl, fi-hydroxyethyl,fi-hydroxyethoxyethyl, B-ethoxyethoxyethyl, acetoxyethoxyethyl, etc.), aphenyl group (e.g., phenyl, tolyl, ethylphenyl, butylphenyl,chlorophenyl, methoxyphenyl, ethoxyphenyl, etc.) and R represents analkyl group of from 2 to 20 carbons (e.g., ethyl, butyl, dodecyl,phytyl, etc.) and an aryl group, such as, a phenyl group (e.g., phenyl,tolyl, methoxyphenyl, ethoxyphenyl, butoxyphenyl, decylphenyl,allylphenyl, etc.) and a naphthyl group (e.g., a-naphthyl, fi-naphthyl,etc.) and preferably where R and R have a total of at least 9 carbonatoms. Typical examples of organic esters of inorganic acids, such as,phosphate esters of Formula I and sulfonate esters of Formula II includethe following:

Triphenyl phosphate Tricresyl phosphate Diphenyl mono-p-tert. butylphenyl phosphate Monophenyl di-p-tert. butyl phenyl phosphate Diphenylmono-o-chlorophenyl phosphate Monophenyl di-o-chlorophenyl phosphateTri-p-tert. butyl phenyl phosphate T ri-o-phenylphenyl phosphateDi-p-tert. butyl phenyl mono (S-tert. butyl-Z-phenylphenyl) phosphateMethyl p-toluenesulfonate Phenyl p-toluenesulfonate Hexylp-toluenesulfonate Methyl methoxybenzenesulfonate Typical examplesoforganic esters of monobasic organic acids of Formulas HI and IVinclude the following:

Ethyl-m-naphthoate Methyl o-methoxybenzoate Butyl o-rnethoxybenzoateu-Naphthyl acetate Tetrahydrofurfuryl benzoate Benzyl benzoate n-Hexylbenzoate Ethyl palmitate Ethyl o-anisate Resorchinol diacetate Ethyleneglycol dilaurate Triacetin Tripropionin Trivalerin Typical examples oforganic esters of dibasic organic acids of Formulas V and VI include thefollowing:

Methyl abietate p-Ethoxyethyl sebacate fl-Ethoxyethyl maleatefi-Ethoxyethyl adipate Tetrahydrofurfuryl succinate Ethyl benzylmalonate Methyl phthalate Ethyl phthalate Propyl phthalate n-Butylphthalate n-Amyl phthalate Iso-amyl phthalate Octyl phthalate Benzylphthalate fl-Methoxyethyl phthalate fl-Ethoxyethyl phthalatefi-Butoxyethylphthalate Typical examples of amides having Formulas VIIand VHI include the following:

Acetyl n-butyl aniline Acetyl methyl p-toluidine Benzoyl piperidineN-amyl succinamide Typical examples of imides of Formula IX include thefollowing:

N-n-amylphthalimide N-n-amyl succinimide N-2-cyanobutylphthalimideTypical examples of ketones of Formula X include the following:

Benzophenone 2,4'-dichlorobenzophenone a-Methoxy acetophenoneAcetophenone 2,4-dihydroxy valerophenone p-Sec.-amylbenzophenone Typicalexamples of alcohols of Formula XI include the following:

Heptadecanol n-Hexanol Octyl alcohol n-Hexylphenylcarbinol fl-(p-tert.butyl phenoxy)-ethyl alcohol Typical examples of ethers of Formula XIIinclude the following:

Ethylene glycol monobenzyl ether Diethylene glycol monobutyl etherDiethylene glycol monobutyl ether monoacetate Diethylene glycolmonoethyl ether Diethylene glycol diethyl ether Ethylene glycolmonophenyl ether Veratrole (1,2-dimethoxybenzene) Eugeneol methyl etherHydroquinonedimethyl ether The metal images, e.g., images made ofpalladium or any metal more easily oxidized (i.e., has a standardoxidation potential more positive than -0.98 volt) (e.g., silver,nickel, copper, iron, palladium, zinc, lead, tin, etc.) in hyrophiliccolloid layers containing a dispersion of one or more of my organic oilsare used to advantage in the preparation of my hight density formazandye images. The metal images are produced in the presence of my organicoils by any conventional image-forming methods and especially byphotographic methods using chemical or physical developing-outphotographic elements and processes.

Silver images, for example, are produced advantageously by developinglatent images in light-sensitive silver salt dispersions in my novelphotographic hydrophilic colloid emulsion in the presence of adispersion of at least one of my organic oils. Any of the silver halideemulsions, e.g., silver chloride, silver bromide, silver iodide, silverchlorobromide, silver bromoiodide, silver chlorobromoiodide, etc., aswell as other light-sensitive silver salts dispersed in gelatin orgelatin substitute and always in the presence of a dispersion of atleast one of my organic oils are used to advantage. These emulsions areadvantageously coated on any of the usual supports, including paper,glass, polymeric films, e.g., cellulose acetate film, polyvinyl acetalfilm, polystyrene film, polypropylene film and other polyolefin films,polycarbonate film, polyethylene terephthalate film and other polyesterfilms.

'Hydrophilic colloids used to advantage in my photographic elementsinclude gelatin, colloidal albumin, a cellulose derivative, or asynthetic resin, for instance, a polyvinyl compound. Some colloids whichmay be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate asdescribed in Lowe, U.S. Pat. 2,286,215, issued June 1 6, 1942; a farhydrolyzed cellulose ester, such as, cellulose acetate hydrolyzed to anacetyl content of 1926% as described in Lowe et al., U.S. Pat.2,327,808, issued Aug. 24, 1943; a water-soluble ethanolamine celluloseacetate as described by Yutzy, U.S. 2,322,085, issued June 15, 1943; apolyacrylamide having a combined acrylamide content of 30-60% and aspecific viscosity of 0.25-1.5 or an imidized polyacrylamide of likeacrylamide content and viscosity as described in Lowe et al., U.S. Pat.2,541,- 474, issued Feb. 13, 1951; zein as described in Lowe, U.S. Pat.2,563,791, issued Aug. 7, 1951, a vinyl alcohol poly mer containingurethane carboxylic acid groups of the type described in Un-ruh et al.,U.S. Pat. 2,768,154, issued Oct. 23, 1956, or containing cyano-acetylgroups, such as, the vinyl alcohol-vinyl cyano-acetate copolymer asdescribed in Unruh et al., U.S. Pat. 2,808,331, issued Oct. 1, 1957; ora polymeric material which results from polymerizing a protein or asaturated acylated protein with a monomer having a vinyl group asdescribed in Illingsworth ct al., U.S. Pat. 2,852,382, issued Sept. 16,195 8.

The emulsions used in the photographic elements of my invention can bechemically sensitized by any of the accepted procedures. The emulsionscan be digested with naturally active gelatin, or sulfur compounds canbe added, such as those described in Sheppard, U.S. Pat. 1,574,944,issued Mar. 2, 1926; Sheppard et al., U.S. Pat. 1,623,499, issued Apr.5, 1927; and Sheppard et al., U.S. Pat. 2,410,689, issued Nov. 5, 1946.

The emulsions can also be treated with salts of the noble metals, suchas ruthenium, rhodium, palladium, iridium and platinum, as described inSmith et al., U.S. Pat. 2,448,060, issued Aug. 31, 1948 and as describedin Trivelli et al., U.S. Pats. 2,566,245 and 2,566,263, both issued Aug.28, 1951.

The emulsions can also be spectrally sensitized with cyanine andmerocyanine dyes, such as those described in Brooker, U.S. Pats.1,846,301 and 1,846,302, both issued Feb. 23, 1932; and 1,942,854,issued Jan. 9, 1934; White, U.S. Pat. 1,990,507, issued Feb. 12, 1935Brooker and White, U.S. Pats. 2,112,140, issued Mar. 22, 1938;2,165,338, issued July 11, 1939; 2,493,747, issued Jan. 10, 1950; and2,739,964, issued Mar. 27, 1956; Brooker et al., US. Pat. 2,493,748,issued Jan. 10, 1950; Sprague, U.S. Pats. 2,503,776, issued Apr. 11,1950 and 2,519,001, issued Aug. 15, 1950; Heseltine et al., U.S. Pat.2,666,761, issued J an. 19, 1954; Heseltine, U.S. Pat. 2,734,900, issuedFeb. 14, 1956; VanLare, U.S. Pat. 2,739,149, issued Mar. 20, 1956; andKodak Limited, British 450,958, accepted July 15, 1936.

The emulsions may also contain speed-increasing compounds of thequaternary ammonium type of Carroll, U.S. Pat. 2,271,623, issued Feb. 3,1942; Carroll et al., U.S. Pat. 2,288,226, issued June 30, 1942; andCarroll et al., U.S. Pat. 2,334,864, issued Nov. 23, 1943; and thepolyethylene glycol type of Carroll et al., U.S. Pat. 2,708,162, issuedMay 10, 1955.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller et al., U.S. Pat. 2,399,- 083, issued Apr. 23, 1946,or stabilized with gold salts as described in Damschroder, U.S. Pat.2,597,856, issued May 27, 1-952; and Yutzy et al., U.S. 2,597,915,issued May 27, 1952. Suitable compounds are potassium chloroaurite,potassium aurithiocyanate, potassium chloroaurate, auric trichloride and2-aurosulfobenzothiazole methochloride.

Latent images produced by the usual image-exposure techniques withinfrared, visible light, ultraviolet, X-rays, etc., are advantageouslydeveloped to silver images by treating with an aqueous alkaline solutionof a developing agent such as hydroquinone, a catechol, a pyrogallol, anaminophenol, a 3-pyrazolidone, etc., followed by fixing in a fixing bathcontaining an alkali metal thiosulfate, thiocyanate or thiourea.

Nickel images, for example, are produced by physically developing anexposed photo-sensitive material of the type containing a layer ofpalladium nuclei on a Ti0 coated support, described in Examples 15 and17 on pages 18 and 19 of Belgian Pat. 718,019.

Any water-soluble difiusible T-salt is used advantageously according tomy invention to convert the metal image to a corresponding formazan dyeimage. Included among the useful T-salts are those having the formulas:

N wish-1 captophenyl group, a nitrophenyl group, etc.), a naphthyl group(e.g., u-naphthyl, B-naphthyl, a carboxynaphthyl group, ahydroxynaphthyl group, a sulfonaphthyl group, a mercaptonaphthyl group,an aminouapht hyl group, a carbamylnaphthyl group, a sulfonamidonaphthylgroup, a sulfamylnaphthyl group, a nitronaphthyl group, etc.) etc., anda heterocyclic group, preferably containing from to 6 atoms, andpreferably containing hetero atoms, such as nitrogen, sulphur, oxygenand selenium, such as, for example, a thiazolyl group, a benzothiazolylgroup, an oxazolyl group, a benzoxazolyl group, a selenazolyl group, abenzoselenazolyl group, a benzimidazolyl group, a naphthimidazolylgroup, a triazinyl group, a pyrimidinyl group, a pyridyl group, aquinolyl group, a thienyl group, etc; R represents any of the groupsrepresented by R and, in addition, represents an alkyl group (e.g.,methyl, butyl, hexyl, dodecyl, mercaptomethyl, mercaptoethyl, etc.)etc., hydrogen, hydroxyl, carboxyl, a salt of a carboxyl group (e.g., analkali metal salt or ammonium salt), a carboxy ester group (e.g.,methoxycarbonyl, ethoxycarbonyl, phenoxycarbonyl, etc.), an amino group(e.g., amino, ethylamino, dimethylamino, anilino, etc.), a carbamylgroup (e.g., carbamyl, ethylcarb-amyl, dimethylcarbamyl, phenylcarbamyl,etc.), sulfo, a salt of a sulfo group (e.g., an alkali metal salt), asulfoamido group (e.g., methylsulfonamido, butylsulfonamido,phenylsulfonamido, etc.), a sulfamyl group (e.g., sulfamyl,methylsulfamyl, butyl sulfamyl, phenylsulfamyl, etc.), the mercaptogroup, the nitro group, or any other substituent cited as being presentin this position of the formazan or the tetrazolium salt in Chem. Rev.55, 355- 483 (.1955); and the substituents R and R advantageouslycontain an electron-sharing group capable of forming metal chelates orcomplexes, such as primary, secondary and tertiary amino, substitutedamino, oxime, thioether, keto, thioketo, hydroxyl, mercapto, carboxyl,sulfo, phospho, alkoxy groups or complexes; X" represents ananion (e.g.,chloride, iodide, bromide, thiocyanate, thiosulfate, sulfate,paratolulenesulfonate, methylsulfate, ethylsulfate, nitrate, acetate,perchlorate, perborate, sulfite, hydroxide, carbonate, etc.); Drepresents a divalent aromatic group (e.g., a phenylene, diphenylene,naphthalene, phenylmet'hylphenyl, etc.); and E rep resents a divalentgroup such as an alkylene group (e.g., methylene, ethylene, propylene,butylene, etc.), an arylene group (e.g., phenylene naphthalene,diphenylene, etc.), an arylene alkylene group, for example, a phenyleneal-kylene group (e.g., phenylene methylene, phenylene butylene,phenylene hexylene, etc.), a naphthylene alkylene group (e.g.,naphthylene methylene, naphthylene butylene, naphthylene propylene,etc.), etc.; q represents an integer of from 1 to 5. #Solutions ofT-salts in which at least one of R R and R represents a thiazolylnucleus, a benzothiazolyl nucleus, a naphthothiazolyl nucleus, abenzimidazolyl nucleus, a naphthimidazolyl nucleus, or a pyridyl nucleusand/or X represents a chloride ion, a bromide ion, an iodide ion, athiocyanate ion or a thiosulfate ion do not require a separate metal ioncomplexing agent for use in converting our metal images to formazan dyeimages; however, a separate complexing agent is used if additionalcomplexing activity is desired.

Tetrazolium salts used to advantage according to my invention includethe following representative compounds:

TABLE-Continued No. T-salt name 82,5-diphenyl-3-(pyrid-3-yl)-2H-tetrazolium chloride.

9 2-(4-ch1orophenyl)-3-(2-chlorophenyl)-5-(pyrid-2-y1)-2H- tetrazoliumiodide.

10 2,3-diphenyl-5-(benzimidazol-Z-yl)-2H-tetrazollum chloride.

11... 2,3-di(4-bromophenyl)-5-(benzothiazol-2-yl)-2H-tetrazoliumchloride. 2-(beuzothiazol-2-yl)-3-phenyl-5-(2-phenyltriezol-5-yl)-2H-tetrazo1i um chloride.

13 2,2-di(benzotniazol-Z-yl)-3,3-diohenyl-5,5-diethylenedi-(2H-tetrazolium chloride).

14... 2,2-di(benzothiazol-2-yl)-3,3-diphenyl-5,5'-di-i,6-hexylenedi-(2H-tetrazolium chloride).

15... 2,2-di (thiazol-fZ-yl)-3,3-dipheny1-5,5-dipheny1ene-di-(ZH-tetrazolium iodide).

17 3,3-di (thiazol-2-yl)-5,5-di(thien-Z-yl)-2,2-di-p-(3,3-dimethoxydiphenylene) di-(ZH-tetrazoliumchloride).

18 3,3,5,5-tetrapheny1-2,2-syn-p-phenylthiourea di-(2H- tetrazoliumbromide).

20 2-(benzothiazol-2-yl)-5-(4-acetamidophenyl)-3(4- phenylazophenyl)-2H-tetrazoli1nn bromide.

21 2-(benzothiazol-2-yl)-3-(4-methoxyphenyl)-5-phenyl-2H- tetrazoliumbromide.

22-.. 2-(4,E-dimethylthiazol-Z-yl) -3,5-dipheny1-2H-tetrazolium bromide.

23 2- (-chlorophenyl) -3-(2-chlorophcnyl) -5- (pyri d-2-yl) -2H-tetrazolium iodide.

24 2-(benzimidazol-2-yl)-5-(2-chlorophenyl)-3-phenyl-2IEI- tetrazolinmchloride.

25 3,5-diphenyl-2-(pyrid-2-yl)-2]E[-tetrazoliu.rn chloride.

26 3-(benzothiazol-2-yl)-5-phenyl-2-(triazin-Z-yl)-2H- tetrazoliumchloride.

27 2,5-di(beuzothiazol-Zyl)3-(p-hydroxyphenyl)-2H- tetrazolium chloride.

28 3-(o-carboxyphenyl)-5-methyl-2-(4-phenylthiazol-Z-yl)- 2H-tetrazoliumbromide.

29 3-(o-carboxyphenyl)-5methyl-Z-(naphthathiazol-Z-yl)- ZH-tetrazoliumchloride.

30.--.. 2- (b enzothi azol-Z-yl) -3-(p-sulfa.mylphenyl) -5-hexyl-2H-tetrezolium chloride.

31 2,3-di(benzothiazol-2-yl) -5-dodecyl-2H-tetrazolium chloride.

32. 2,3-di (pyrid-Z-yl)-5-hydroxy-2Htetrazol.um chloride.

33- 2,3-di(benzimidazol-Z-yl)-5 mercapto 2H-tetrazolium bromide.

84. fi-arkrxilin o( 13(benzothiazp l-2-yl) -2phenyi-2H-tetrazolium c one.

35 fi-benzamido-3-(4,5-dimethylthiazo1-2-yl)2-phenyl-2H- tetrazoliumchloride 39 2-(benzothiazol-2-yl)-5-(Z-chlorophenyl)-3-(4-nitrophenyl)-2H-tet'razelium bromide.

40 2-(benzothiazol-2-yl)-5-phenyl-3-(4-to1yl)-2H-tetrazolium bromide.

41 2-(benzothiazol-2-yD-3-(4-chloropheny1)-5-phenyl-2H- tetrazoliumbromide.

42 Z-(benzothiazol-Z-yl)-5(4-chlorophenyl)-3 (4'nitrophenyl)ZH-tctrazolium bromide.

43 3-gaenzoghi azol-2-yl) -2-phenyl-5-(quinol-Z-yl) -2H-tetrazolium 44B-(benzothiazol-Z-yl)-2-phenyl-5-propyl-2H-tetrazolium iodide.

45 B-(benzothiazol-Z-yl) -2-phenyl-5-(pyrimidine-2-y1) -2H- tetrazoliumbromide.

46 2-(naphthimidazol-2-yl)3,5-diphenyl-2H-tetrazolium acetate.

47- B-(benZirnidaZOLZ-yl)-2,5-diphenyl-ZH-tetrazolium nitrate.

48- 3,5-diphenyl-2-(pyrid-2-yl)-2H-tetrezolium sulfate.

49 2,5-dipdhenyl-3(4,5-dimethy1thiazol-2-vl)-2H-tetrazolium iodi e.

50 2,3-diphenyl-2Htetrazolium thiosulfatc.

51 2,B-diphenyl-ZH-tetrezoliurn thiocyanate.

52 2,3,5-triphenyl-2H-tetrazolium chloride.

53 2,3-diphenyl-2H-tetrazolium chloride.

54 2,3-diphenyl-2H-tetrazolium iodide.

55 2,3-diphenyl-5-methyl-2H-tetrazolium chloride.-

56 2,3-diphenyl-5-methyl-ZH-tetrazolium bromide.

57 3-(ril-fiyii'oxyphenyl)-5-methyl-Z-phenyl-ZH-tetrazolium c or e.

58 3-(ril-isulfamylphenyl)-5-mcthyI-2-phenyl-ZH-tetrazolium c o e.

59 2,3-diphenyl-5-ethyl-2H-tertazo1ium chloride.

60 3(-pk-1slu1a1mylphenyl)-3-phenyl-5-propyl-ZH-tetrazolium c or. e.

61 2,3-diphenyl-5-isobutyl-ZH-tetrazolium chloride.

62- I 2,S-diphenyl-fi-n-hexyl-2H-tetrazolium chloride.

63 2,3-diphenyl fi-dodecyl-2Htetrazoliu.m chloride.

64 2,3-diphenyl-5-hydroxy-ZH-tetrazolium betaine.

65 2,3-diphenyl-5-hydroxy-2H-tetrazelium chloride.

66 2,3-diphenyl-5-mereapto-2H-tetrazolium betaine.

67 5-amino-2,3-dipheny1-2H-tetre.zolium chloride.

68 5-benzamido-2,3-diphenyl-2H-tetrezolium chloride.

69 B-benzamido-2,3-diphenyl-2H-tetrazolium betaine.

70 5-cyano-2,3-diphenyl-2H-tetrazollum chloride.

71 5-carboxy-2,3-diphenyi-2H-tetrazolium betaine.

72 E-carboxy-2,3-diphenyl-ZH-tetrazolium chloride.

73 5-carboxy-2,3-diphenyl-2H-tetrazolium nitrate.

74 5-ethoxycarbonyl-2,3-diphenyl-2H-tetrazolium chloride.

76 23-12111-(pdethoxyphenyl)-5-ethoxycarbonyl-2H-tetrazolium c or e.

77- 5-acetyl-2,3-diphenyl-2H-tetrazolium chloride.

78 5-benzoyl-2,3-diphenyl-2H-tetrazolium chloride.

79 2,5-dipheuyl-3-(p-tolyl)-2H-tetrazolinm bromide.

80 2,5-dipheny1-3-(p-isopropylphenyl)-2H-tetrazolium bromide.

TABLEContlnued T-salt No. T-salt name 812,5-dipheny1-3-(p-n-dodecylphenyl)2H-tetrazolium iodide. 822,5-diphenyl-3-(p diphenyl)-2H-tetrazoluim chloride.

2,3-diphenyl-5-(p-diphenyl)-2H-tetrazolium chloride.

84 2,5-diphenyl-3-(p-chlorophenyl)-2H-tetrazolium iodide.

85 2,5-diphenyl-s-(iodophenyl)-2H-tetrazolium chloride.

86- 3,5-d1(p-bromophenyl)-2-phenyl-2H-tetrlazolium chloride.

87 5-(p.bromophenyl)-2-phenyl-3-(2,4,6-tr1bromophenyl)-2H- tetrazoliumbromide.

88 B-(p-lodophenyl)-2-(p-nitrophenyl)-5-phenyl-2H-tetrazolium 1Ochloride.

89 3-(p-hydroxyphenyl)-5-(p-nitrophenyl)-2-phenyl-2H-tetrazoliuinchloride.

90 5-(8,4dimethoxypheny1)-3-methoxyphenyl-2-phenyl-2H- tetrazoliumiodide.

5-(3-methoxyphenyl) -3-(a-triiiuoromethylphenyl)-2-phenylzH-tetrazoliumacetate.

92 5-(4-eyanophenyl)-2,B-diphenyl-ZH-tctrazolium chloride.

- 5-(fur-2-yl)-2,3-dlphenyl-2H-tetrazollum chloride.

.. 2,3-diphenyl5-n1tro-2H-tetrazolium chloride.

107 2,3-diplienyl-5-sulfo-2H-tetrazolium chloride.

108- 2,3-diphenyl-5-sulfonamido-ZH-tetrazolium chloride.

109 2,2'fi,figegraphenyl-5,5-diethylene di-(2H-tetrazolium 1112,2h?,3fietraphenyl-5,5-di-p-phenylene dl-(2H-tetrazo1ium c or 1125,5'-dimethyl;3,3-diphenyl-2,2'-di-p-diphonylene di-(ZH- tetrazolium,(lllOlldB) 113 3,3,5,5-tetrap enyl-2,2'-di-p-(3,3-dimethyl-diphenylene)di-(ZH-tetrazolium chloride).

114 3,3,5,5-tetraphenyl-2,2-syn-p-phenylthiourea di-(ZH- tetrazoliumchloride).

115 3,3',5,5-tetraphenyl-2,2-syn-p-phenyl sulfoxide di-(2H- tetrazoliumchloride) 116 2,2',3,3-tetraphenyl-5,5'-p-phenylene ethylene di-(ZH-tetrazolium chloride.

These tetr'azolium salts are well known in the art, most of them havingbeen described in literature references such as Chemical Revue 55,published bi-monthly 5 for the American Chemical Society by the Williamsand Wilkins Co., Baltimore, 1955. Any tetrazolium salts that are notshown specifically in the prior art are advantageously prepared bymethods well known in the art.

When aqueous solutions of my T-salts are brought into contact with metalimages of palladium or any metal more easily oxidized (i.e., has astandard oxidation potential more positive than -0.98 volt) (e.g.,silver, nickel, copper, iron, palladium, zinc, lead, tin, etc.), themetal is oxidized to its ion and the T-salt is reduced to produce thecorresponding formazan dye. The following equation shows a typicalreaction:

Formazan Dye Any ligand that is a silver complexing agent isadvantageously used that produces a silver ion complex.

Included among the ligands used to advantage are the following typicalexamples: water-soluble thiosulfates (e.g., sodium thiosulfate,potassium thiosulfate, ammonium thiosulfate, etc.), thiourea,ethylenethiourea, a water-soluble thiocyanate (e.g., sodium thiocyanate,potassium thiocyanate, ammonium thiocyanate), a watersoluble sulfurcontaining dibasic acid. Water-soluble diols used to advantage includethose having the formula:

wherein r is an integer of from 2 to 13; the Zfs represent oxygen orsulfur atoms such that at least one-third of the Z atoms are sulfur andthere are at least two consecutive Z s in the structure of the compoundwhich are sulfur atoms. The diols advantageously used are also includedin comp ounds having the formula:

wherein X and X represent oxygen or sulfur, such that when X representsoxygen, X represents sulfur and when X represents sulfur, X representsoxygen; 0, d, e, f and g each represent an integer of from 1 to 15, suchthat the sum of c+d+e+f+g represents an integer of from 6 to 19, andsuch that at least one third of the total of all the X s plus all the Xs represent sulfur atoms and at least two consecutive X s and/or X s inthe structure of the compound are sulfur atoms.

Typical diols include the following:

(1) 3,6-dithia-l,8-octanedio1 HOCH CH SCH CH SCH CH OH (2)3,6,9-trithia-l,1 l-undecanediol HOCH CH SCH CH SCH CH SCH CH OH (3)3,6,9,12-tetrathia-1,14-tetradecanediol HO (CH CH S CH CH OH (4) 9-oxa-3,6,9,12,15-tetrathia-1,17-heptadecanediol HO (CH CH S CH CH O (CH CH S)CH C-H OH (5) 9, 12-dioxa-3,6, 15,18-tetrathia-1,20-eicosanediol HO(CHCH S) 2 (CH CH O (CH CH S CH CH O-H (6)3,6-dioxa-9,12-dithia-l,14-tetradecanediol HO(CH CH O 2 (CH CH S) CH CHOH (7) 3,12-dioxa-6,9-ditl1ia-1,l4-tetradecanediol 'HOCH CH O (CH CH S)CH CH OCH CH OH (8) 3,l8-dioxa-6,9,12,1S-tetrathia-1,20-eicosanediolHOCH CH O CH CH S) CH CH O CH CH OH (9)12,l8-dioxa-3,6,9,15,21,24,27-heptathia-1,29-nonacosanediol l0)6,9,15,18-tetrathia-3,12,2l-trioxa-1,23-tricosanedi0l HOCH CH O(CHzCHgS) CH CH O (CH CH S) CH CH OCH CH OH Water-soluble sulfurcontaining dibasic acids used to advantage include those having theformula:

HOOCCH (SCH CH SCI-I COOH in which 1 represents an integer of from 1 to,and includmg, 3 and the alkali metal and ammonium salts of said acids.Typical illustrative examples include:

ethylene-bis-thioglycolic acid HOOCCH SCH CH SCH CO0H3,6,9-trithiahendecanedioic acid HOOCCH (SCH CH SCH COOH3,6,9,l2-tetrathiatetradecanedioic acid 13 nooccnnscu cun scn coonethylene-bis-thioglycolic acid di-soclium salt ethylene-bis-thioglyco1icacid di-potassium salt ethylene-bis-thioglycolic acid di-ammonium salt3,6,9-trithiahendecanedioic acid di-sodium salt3,6,9,12-tetrathiatetradecanedioic acid di-sodium salt The concentrationof the T-salt and the ligand in my compositions can be variedconsiderably, with an operable range of concentrations extending fromthe solubility limit of the T-salt and the solubility limit of theligand down to a minimum concentration where the overall reactionpotential for the specific T-salt, ligand and specific metal image justremains positive, usually above +0.01 volt. The operable concentrationranges and the preferred concentration ranges are readily determined bymethods well known in the art and need not be discussed further.

The following examples are included for a further understanding of myinvention:

EXAMPLE 1 Dispersions identified as A, B, C and D are made having thecompositions indicated below for high-boiling crystalloidal onganic oilsA, B, C and D, respectively, as identified below:

Organic oil g 44.0 10% gelatin solution g 220.0 Alkanol B c 4.4

Mill 5 times, then add distilled Water to a total weight of 300 g. Theaverage diameter of the oil particles is about 1 11.

Each of the dispersions A, B, C and D are blended with separate portionsof a gelatino silver bromoiodide emulsion and each of these blends isfurther blended with a formaldehyde solution just before coating on eachside of a polyethylene terephthalate support using the coating techniquedual melting as described in US. Pat. 2,912,343 so that there is coatedon each side of the support per square foot 175 mg. of silver, 134 mg.of gelatin and 89 mg. of organic oil. Each coating is identifiedaccording to the identification of the organic oil used. Control CoatingX is made just like the other coatings, but by substituting for theorganic oil dispersion suflicient gelatin so that the control coatinghas in each square foot on each side of the support 134 mg. of gelatinand 175 mg. of silver. After the coatings are dried, strips of thecoatings are sensitometrically exposed to light with a sensitometer andprocessed at 35 C. with six minutes development in a conventionalaqueous alkaline developer solution containing p-methylaminophenol andhydroquinone, five minutes fixing in the fixing bath described later inthis example, washing and drying. The dried and processed strips areeach cut in half so that each half of a strip contains identical silverimages. One-half of each of the strips are given no further treatmentwhile the other half are given the following additional process steps ata temperature of 35 C.:

The T-salt bath has the composition:

2,3,5-triphenyl-2H-tetrazoliumchloride g 15 Thiourea g 15 Sodiumthiosulfate g 50 Distilled water to make 1 l.

The fixing bath has the composition:

Sodium thiosulfate g 2400 Sodium sulfite (desiccated) g 15.0 Aceticacid, 28% cc 48.0 Boric acid crystals g 7.5 Potassium alum g 15.0

Water to 1.0 l.

The densities of the silver images in the halves of the strips ofprocessed Coatings X, A, B, C and D that were not given the T-salt bathtreatment are measured with a densitometer and from these data the -Dand fog values are recorded and the gamma and relative speed values arecomputed with the relative speed of the Control Strip X arbitrarily setat and the relative speeds for Strips A, B, C and D related to therelative speed set for the control. The densities of the silver plusformazan dye images in the other half of the strips of processedCoatings X, A, B, C and D that were given the T-salt bath treatment aremeasured with a densitometer and from these data the D and fog valuesare recorded and the gamma and relative speed values are computed withthe relative speed values related to the relative speed of 100 set forControl Coatings X (without T-salt bath treatment). The percent increasein relative speed, 7 and D produced in Strips X, A, B, C and D bytreatment with the T-salt bath are tabulated in Table II:

TABLE II Percent increase in- Rel. speed '7 from Dmux from Organic fromT-salt T-salt bath T-salt bath oil bath treatment treatment treatmentNone 23 20 23 A 41 91 81 B 54 100 103 C 68 69 D 58 41 The data in TableIII show very substantially higher percent increases in D and 7 fromtreatment of my silver images in the presence of organic oils A, B, Cand D with the T-salt bath compared to treatment of the silver image inthe control strip containing no organic oil. Strips A and B with organicoils A and B, respectively, have substantially higher percent increasein relative speed from treatment with the T-salt bath than is shown withthe same T-salt bath in Control Strip X without any organic oil. Ananalysis is made of the amount of silver in each of the Strips X, A, B,C and D, both those strips that were given the T-salt bath treatment aswell as those without the T-salt bath treatment. The decrease in silvercaused by T-salt bath treatment in Coatings X, A, B, C and D iscalculated and recorded in Table III. The increase in 13 densityproduced by T-salt bath treatment is determined for each coating andrecorded in Table III. The change in covering power==Increase in D x 10/L0ss in Ag produced by the T-salt bath treatment is calculated andrecorded in Table III for each coating.

TABLE III Covering Loss in Increase in power in- Ag from Dmnx fromcrease from Organic T-salt bath T-salt bath T-salt bath Coating oiltreatment treatment treatment X.- None.--- 79 0.28 3.5 A 142 1.01 7. 1 B1.26 6. 5 169 0. 84 5. 0 83 0.48 5.8

The data in Table III show that the addition of my organic oils A, B, Cand D to my photographic emulsions increases the amount of silverutilized in the conversion 15 of silver metal image to formazan dyeimage resulting in a very substantial increase in optical density and incovering power. The presence of Organic Oil A in my Coating A results intwice the increase in covering power produced by the same T-salt bathtreatment in Control Coating X without an organic oil.

EXAMPLE 2 Example 1 is repeated exactly, except that the Coatings X, A,B, C and D are sensitometrically exposed with X-rays instead of light toproduce comparable latent images. The results obtained are identical tothose obtained in Example 1.

EXAMPLE 3 Example 1 is repeated, except that the T-salt bath used is 24C. instead of 35 C. and the treatment time increased enough to produce asilver plus formazan dye image in the Control Coating X that isequivalent to the silver plus formazan dye image produced in ControlCoating X in Example 1. The data show that treatment with the T-saltbath produces in my elements improvements in covering power, D 'y andspeed that are similar to those obtained in Example 1.

EXAMPLE 4 Thirteen sets of strips of Coatings A, B, C and D of myinvention and Control Coating X are prepared, sensitometrically exposed,developed, fixed, washed, dried and slit, all as described in Example 1.One-half of each of these processed strips is given no further treatmentand the other half is presoaked, treated with T-salt solution bath,fixed, washed and dried as described in Example 1, except that each setof Strips A, B, C, D and X are put through a T-salt bath of Example 1,but in which the 2,3,5-triphenyl-2H-tetrazolium chloride (of Example 1)is replaced by 15 g. of a different T-salt from the following list:

2,3-dipheny1-5- (pyrid-Z-yl -2H-tetrazolium bromide 2,3-diphenyl-5-(benzoxazol-Z-yl) -2H-tetrazolium chloride 2,3 -di (4-bromophenyl -5-(benzothiazol-Z-yl) -2H- tetrazolium chloride 5 ,5 '-dimethyl-3 ,3'-diphenyl-2,2'-di (p-diphenylene di (ZH-tetrazolium chloride) T-SaltName 2,2',3,3-tetraphenyl-S,5-diethylene-di(2H- tetrazolium chloride)2,3'-diphenyl-ZH-tetrazolium chloride 3- (p-hydroxyphenyl)-5-methyl-2H-tetrazolium chloride 2,3-diphenyl-5-dodecyl-2H-tetrazoliumchloride 2,3-diphenyl-S-hydroxy-ZH-tetrazolium chloride5-amino-2,3-diphenyl2H-tetrazolium chloride5-carboxy-2,3-diphenyl-2H-tetrazolium chlorideS-benzamido-2,3-diphenyl-2H-tetrazolium chloride5-ethoxycarbonyl-2,3-diphenyl-2H-tetrazolium chloride D 7, relativespeed and covering power data are obtained for each half of the thirteensets of Coatings A, B, C, D and X, as described in Example 1. The datafor each set of coatings show that my Coatings A, B, C and D givesubstantially the same increases in covering power, D 'y, and relativespeed from treatment in the T-salt baths using the T-salts of thisexample as are obtained for Coatings A, B, C and D, respectively, fromthe treatment with the T-salt bath described in Example 1.

EXAMPLE 5 Example 1 is repeated, but the dispersions of organic oil areprepared so that the average diameters of the oil particles is about2,11. instead of l,u.. Improvements in cover- 1 6 ing power, D 'y, andrelative speed, similar to those in Example 1, are obtained.

EXAMPLE 6 Example 1 is repeated, except that the formulation of theorganic oil dispersions is altered so that the weight ratio of organicoil to gelatin in the coated elements is about 1:0.1 instead of the 1:15weight ratio used in Example 1. The results show that these elementsprovide useful improvements in image covering power, D 'y, and relativespeed over the control without any organic oil when developed and fixedsilver images in these elements are treated with the T-salt bath.

EXAMPLE 7 Example 1 is repeated, except that the formulation of theorganic oil dispersions is altered so that the weight ratio of organicoil to gelatin is about 1:30 instead of 1:1.5, as in Example 1. Theresults show that these elements of my invention provide usefulimprovements over the control when treated with the T-salt bath.

EXAMPLE 8 Example 1 is repeated, except that instead of the organic oilsused in Example 1, the other phosphate esters and sulfonate esterslisted on page 10 of this application, the organic esters listed onpages 11 and 12, the amides, the imides, the ketones, the alcohols, alllisted on page 12, and the ethers listed on page 13, are used as theorganic oil. Silver images in my elements containing dispersions ofthese organic oils are converted to silver plus formazan dye images withsubstantially greater increases in covering power by treatment with theT-salt bath than the increase in covering power produced in silverimages in the control elements by the same treatment.

Similarly, it can be shown that elements of my invention containingdispersions of still other organic oils of Formulas I through XII willgive greater increases in image covering power than a correspondingcontrol when metal images such as silver, nickel, copper, ironpalladium, zinc, lead, tin, etc. are treated with a T-salt bathcontaining a T-salt and a metal complexing agent.

Similarly, it can be shown that any of my photographic elements, such asare described in Example 1, are advantageously treated with T-salt bathsusing any of the specific T-salt Numbers 1 through 117 in my process toproduce silver plus formazan dye images having substantially highercovering power than the silver plus formazan dye images produced in acontrol element containing none of my dispersed organic oil.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. In the process of replacing at least a portion of a photographicmetal image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said metal image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said metal image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high boiling, substantiallycolorless, crystalloidal, organic oil having molecules that contain atleast one polar group selected from the class consisting of an estergroup, an amide group, an imide group, a ketone group, a hydroxyl group,an oxygen ether group and a halogen atom.

2. The process of claim 1 in which said binder comprises gelatincontaining said organic oil as dispersed particles having diameters inthe range up to about 2 3. The process of claim 1 in which said bindercomprises gelatin containing a dispersion of said organic oil 17 inwhich the ratio of said oil to said gelatin is in the range of fromabout 1:0.1 to about 1:30.

4. In the process of replacing at least a portion of a photographicsilver image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said silver image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said silver image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high-boiling, substantiallycolorless, crystalloidal, organic oil selected from those having theformulas:

wherein R R R R R and R each represent a member independently selectedfrom the class consisting of hydrogen, halogen, an alkyl group, a phenylgroup, an alkoxy group and a phenoxy group;

II. R2

g -ORQ R A wherein R and R are as defined previously and R represents agroup selected from the class consisting of an alkyl group and an arylgroup;

III. 0

R7-O R3 group and a group R and R are as defined previously and nrepresents an integer of from 2 to 3;

wherein R is as described previously; R represents a group selected fromthe class consisting of an alkyl group and an aryl group; Z represents adivalent group selected from the class consisting of CH=CH and-(CH2)mand m represents an integer from 1 to 10;

iii-0R o iii-O R0 wherein R and R are as defined previously, and Rrepresents a member selected from the class consisting of hydrogen, analkyl group, an alkoxy group and a halogen atom;

VII. Ru

wherein Z, R and R are as defined previously, and R and R each representa member independently selected from the class consisting of hydrogen,an alkyl group, an aryl group, and nonmetallic atoms which, when takentogether with the nitrogen atom, between them complete a 5- to6-membered heterocyclic ring;

wherein R is as defined previously and D represents a divalent groupselected from the class consisting of a (CH),, group, CH=CH-, a Braggroup I a R group, a B; group io a 2 an integer of from 1 to 3, and R isas defined previously; X

-' p, 9 represents wherein R, is as defined previously and R representsa group selected from the class consisting of an alkyl group and an arylgroup;

(XI) R -OH wherein R represents a group selected from the classconsisting of an alkyl group and a 4-alkylaryl group; and

wherein R represents a group selected from the class consisting of analkyl group, and a phenyl group; and R represents a group selected fromthe class consisting of an alkyl group and a phenyl group.

5. The process of claim 4 in which said binder comprises gelatincontaining said organic oil as dispersed particles having diameters inthe range of up to about 2 6. The process of claim 4 in which saidbinder comprises gelatin containing a dispersion of said organic oil inwhich the ratio of said oil to said gelatin is in the range of fromabout 1:0.1 to about 1:30.

7. In the process of replacing at least a portion of a photographicsilver image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said silver image has a standard oxidation potential morepositive than -0.=98 volt and reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said silver image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high-boiling, substantiallycolorless, crystalloidal, organic oil selected from those having theformula:

wherein R R R R R and R each represent a member independently selectedfrom the class consisting of hydrogen, halogen,= an alkyl group, aphenyl group, an alkoxy group and a phenoxy group.

8. In the process of replacing at least a portion of a photographicsilver image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said silver image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said silver image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high-boiling, substantiallycolorless, crystalloidal, organic oil selected from those having theformula:

wherein R and R are each independently selected from the classconsisting of an alkyl group and an aryl group, and R10 represents amember selected from the class consisting of hydrogen, an alkyl group,an alkoxy group and a halogen atom.

9. In the process of replacing at least a portion of a photographicsilver image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said silver image reduces a tetrazolium salt to form saidformazan dye and a metal complexin-g ligand forms a metal complex, theimprovement wherein said replacement of said silver image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high-boiling, substantiallycolorless, crystalloidal, organic oil selected from those having theformula:

R1; R1 /N wherein R represents a group selected from the classconsisting of an alkyl group and an aryl group; R and R each represent amember independently selected from the class consisting of hydrogen, analkyl group, an aryl group and nonmetallic atoms which, when takentogether with the nitrogen atom, between them complete a to G-memberedheterocyclic ring.

10. In the process of replacing at least a portion of a photographicsilver image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said silver image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said silver image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of at least one high-boiling, substantiallycolorless, crystalloidal, organic oil selected from those having theformula:

R -OH wherein R represents a group selected from the class consisting ofan alkyl group and a 4-alkylaryl group.

11. In the process of replacing at least a portion of a photographicmetal image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said metal image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said metal image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of tricresyl phosphate with the weight ratio oftricresyl phosphate to gelatin being about 1:1.5.

12. In the process of replacing at least a portion of a photographicmetal image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said metal image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said metal image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of di-n-butyl phthalate with the weight ratio ofdi-nbutyl phthalate to gelatin being about 1: 1.5.

13. In the process of replacing at least a portion of a photographicmetal image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said metal image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said metal image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of diethyl lauramide with the weight ratio ofdiethyl lauramide to gelatin being about 1:15.

14. In the process of replacing at least a portion of a photographicmetal image in a hydrophilic colloid binder layer with a formazan dyeimage, wherein said metal image reduces a tetrazolium salt to form saidformazan dye and a metal complexing ligand forms a metal complex, theimprovement wherein said replacement of said metal image with saidformazan dye image is conducted in a hydrophilic colloid binder layercontaining a dispersion of 2,4-di-tert-amylphenol with the weight ratioof di-tert-amylphenol to gelatin being about 1:15.

References Cited UNITED STATES PATENTS 2,949,360 8/1960 Julian 96-4003,185,567 5/1965 Rogers 963 3,257,205 6/1966 Cassiers 9695 3,287,13211/1966 Hunt 96-20 3,438,776 4/ 1969 Yudelson 96-28 3,503,741 3/1970Wilson 9699 3,519,428 7/ 1970 Ishikawa 9695 3,576,634 4/1971 Woodward96-66 FOREIGN PATENTS 884,494 12/ 1961 Great Britain 96-84 NORMAN G.TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner US. Cl.X.R. 9667

